1. Field of The Invention
The present invention relates to a control system for an actuator applicable to a servo system in which a low resolution sensor is used and/or an operation detection signal having a large number of noise components is used for a feedback signal.
2. Description of the Background Art
A Japanese paper titled "Robust Control for Automotive Actuator" which is announced in the "Tenth adaptive control symposium" (held from Jan. 31, 1990 to Feb. 2, 1990 in Tokyo, Japan) exemplifies a previously proposed actuator control system.
In the disclosed actuator control system, a method of controlling the actuator of a DC motor type four-tire-wheel steering actuator includes a model adaptive control to which a robust compensator is used to achieve a robust control against the disturbance so that influences of the disturbance and frictional motion of the actuator itself can hardly be received.
However, since a sensor providing a low resolution and great number of noise components is used as operation detection means for the actuator in the actuator control system disclosed in the above-identified Japanese Paper, a motor current command value i.sup.* supplied to the DC motor to drive the actuator violently vibrates, a simulation result of which is shown in FIG. 4 (A). Then, this vibration causes the actuator itself to be vibrated and an abnormal sound is generated therefrom.
In addition, in a case where a low pass filter having a low cut-off frequency is used to eliminate sensor noises, a response of the actuator becomes vibratile due to an insufficient damping force of the control system when the command value i.sup.* is abruptly changed, as appreciated from a simulation result shown in FIG. 5 (B).